Our understanding of the rock art created by the San people of southern Africa over many centuries is helped by written accounts, so that what first appears to be an image of a hunting expedition becomes a record of a spiritual journey into another realm of experience.

"For many years it was a matter of gaze and guess," says David Lewis Williams, an authority on rock art: "You gaze at it, and if you gaze long enough, your guess will take you close to what it's all about - and I'm afraid that's not the case, but we don't have to gaze and guess anymore."

Listen to this episode from the BBC which features South African San rock art. The link allows you to listen to earlier and later episodes as well: